A Message Splitter implementation that invokes the specified method
on the given object. The method's return value will be split if it
is a Collection or Array. If the return value is not a Collection or
Array, then the single Object will be returned as the payload of a
single reply Message.

splitMessage

Subclasses must override this method to split the received Message. The return value may be a Collection or
Array. The individual elements may be Messages, but it is not necessary. If the elements are not Messages, each
will be provided as the payload of a Message. It is also acceptable to return a single Object or Message. In that
case, a single reply Message will be produced.